[3.12] gh-115528: Update language reference for PEP 646 (GH-121181) #124633
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To recap: the objective is to make starred expressions valid in `subscription`,
which is used for generics: `Generic[...]`, `list[...]`, etc.
What _is_ gramatically valid in such contexts? Seemingly any of the following.
(At least, none of the following throw `SyntaxError` in a 3.12.3 REPL.)
Generic[x]
Generic[*x]
Generic[*x, y]
Generic[y, *x]
Generic[x := 1]
Generic[x := 1, y := 2]
So introducting
flexible_expression: expression | assignment_expression | starred_item
end then switching `subscription` to use `flexible_expression` sorts that.
But then we need to field `yield` - for which any of the following are
apparently valid:
yield x
yield x,
yield x, y
yield *x,
yield *x, *y
Introducing a separate `yield_list` is the simplest way I've been figure out to
do this - separating out the special case of `starred_item ,`.
(cherry picked from commit 7d3497f)
Co-authored-by: Matthew Rahtz <matthew.rahtz@gmail.com>
Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>
This was referenced Sep 26, 2024
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To recap: the objective is to make starred expressions valid in
subscription,which is used for generics:
Generic[...],list[...], etc.What is gramatically valid in such contexts? Seemingly any of the following.
(At least, none of the following throw
SyntaxErrorin a 3.12.3 REPL.)So introducting
end then switching
subscriptionto useflexible_expressionsorts that.But then we need to field
yield- for which any of the following areapparently valid:
Introducing a separate
yield_listis the simplest way I've been figure out todo this - separating out the special case of
starred_item ,.(cherry picked from commit 7d3497f)
Co-authored-by: Matthew Rahtz matthew.rahtz@gmail.com
Co-authored-by: Jelle Zijlstra jelle.zijlstra@gmail.com
📚 Documentation preview 📚: https://cpython-previews--124633.org.readthedocs.build/